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Das A, Charpentier O, Hessin C, Schleinitz J, Pianca D, Le Breton N, Choua S, Grimaud L, Gourlaouen C, Desage-El Murr M. Site-Selective Radical Aromatic C-H Functionalization of Alloxazine and Flavin through Ground-State Single Electron Transfer. Angew Chem Int Ed Engl 2024; 63:e202403417. [PMID: 38627209 DOI: 10.1002/anie.202403417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Indexed: 06/11/2024]
Abstract
Flavins and their alloxazine isomers are key chemical scaffolds for bioinspired electron transfer strategies. Their properties can be fine-tuned by functional groups, which must be introduced at an early stage of the synthesis as their aromatic ring is inert towards post-functionalization. We show that the introduction of a remote metal-binding redox site on alloxazine and flavin activates their aromatic ring towards direct C-H functionalization. Mechanistic studies are consistent with a synthetic sequence involving ground-state single electron transfer (SET) with an electrophilic source followed by radical-radical coupling. This unprecedented reactivity opens new opportunities in molecular editing of flavins by direct aromatic post-functionalization and the utility of the method is demonstrated with the site-selective C6 functionalization of alloxazine and flavin with a CF3 group, Br or Cl, that can be further elaborated into OH and aryl for chemical diversification.
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Affiliation(s)
- Agnideep Das
- Université de Strasbourg, Institut de Chimie, CNRS UMR7177, 4, rue Blaise Pascal, 67000, Strasbourg, France
| | - Oscar Charpentier
- Université de Strasbourg, Institut de Chimie, CNRS UMR7177, 4, rue Blaise Pascal, 67000, Strasbourg, France
| | - Cheriehan Hessin
- Université de Strasbourg, Institut de Chimie, CNRS UMR7177, 4, rue Blaise Pascal, 67000, Strasbourg, France
| | - Jules Schleinitz
- Laboratoire des biomolécules, LBM, Chemistry department École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France
| | - David Pianca
- Université de Strasbourg, Institut de Chimie, CNRS UMR7177, 4, rue Blaise Pascal, 67000, Strasbourg, France
| | - Nolwenn Le Breton
- Université de Strasbourg, Institut de Chimie, CNRS UMR7177, 4, rue Blaise Pascal, 67000, Strasbourg, France
| | - Sylvie Choua
- Université de Strasbourg, Institut de Chimie, CNRS UMR7177, 4, rue Blaise Pascal, 67000, Strasbourg, France
| | - Laurence Grimaud
- Laboratoire des biomolécules, LBM, Chemistry department École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France
| | - Christophe Gourlaouen
- Université de Strasbourg, Institut de Chimie, CNRS UMR7177, 4, rue Blaise Pascal, 67000, Strasbourg, France
| | - Marine Desage-El Murr
- Université de Strasbourg, Institut de Chimie, CNRS UMR7177, 4, rue Blaise Pascal, 67000, Strasbourg, France
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2
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Zubova E, Pokluda A, Dvořáková H, Krupička M, Cibulka R. Exploring the Reactivity of Flavins with Nucleophiles Using a Theoretical and Experimental Approach. Chempluschem 2023:e202300547. [PMID: 38064649 DOI: 10.1002/cplu.202300547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 11/30/2023] [Indexed: 01/13/2024]
Abstract
Covalent adducts of flavin cofactors with nucleophiles play an important role in non-canonical function of flavoenzymes as well as in flavin-based catalysis. Herein, the interaction of flavin derivatives including substituted flavins (isoalloxazines), 1,10-ethylene-bridged flavinium salts, and non-substituted alloxazine and deazaflavin with selected nucleophiles was investigated using an experimental and computational approach. Triphenylphosphine or trimethylphosphine, 1-nitroethan-1-ide, and methoxide were selected as representatives of neutral soft, anionic soft, and hard nucleophiles, respectively. The interactions were investigated using UV/Vis and 1 H NMR spectroscopy as well as by DFT calculations. The position of nucleophilic attack estimated using the calculated Gibbs free energy values was found to correspond with the experimental data, favouring the addition of phosphine and 1-nitroethan-1-ide into position N(5) and methoxide into position C(10a) of 1,10-ethylene-bridged flavinium salts. The calculated Gibbs free energy values were found to correlate with the experimental redox potentials of the flavin derivatives tested. These findings can be utilized as valuable tools for the design of artificial flavin-based catalytic systems or investigating the mechanism of flavoenzymes.
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Affiliation(s)
- Ekaterina Zubova
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic
| | - Adam Pokluda
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic
| | - Hana Dvořáková
- Central Laboratories, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic
| | - Martin Krupička
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic
| | - Radek Cibulka
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic
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3
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Uleanya KO, Anstöter CS, Dessent CEH. Photodissociative decay pathways of the flavin mononucleotide anion and its complexes with tryptophan and glutamic acid. Phys Chem Chem Phys 2023; 25:30697-30707. [PMID: 37934009 DOI: 10.1039/d3cp04359b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
Flavin mononucleotide (FMN) is a highly versatile biological chromophore involved in a range of biochemical pathways including blue-light sensing proteins and the control of circadian rhythms. Questions exist about the effect of local amino acids on the electronic properties and photophysics of the chromophore. Using gas-phase anion laser photodissociation spectroscopy, we have measured the intrinsic electronic spectroscopy (3.1-5.7 eV) and accompanying photodissociative decay pathways of the native deprotonated form of FMN, i.e. [FMN-H]- complexed with the amino acids tryptophan (TRP) and glutamic acid (GLU), i.e. [FMN-H]-·TRP and [FMN-H]-·GLU, to investigate the extent to which these amino acids perturb the electronic properties and photodynamics of the [FMN-H]- chromophore. The overall photodepletion profiles of [FMN-H]-·TRP and [FMN-H]-·GLU are similar to that of the monomer, revealing that amino acid complexation occurs without significant spectral shifting of the [FMN-H]- electronic excitations over this region. Both [FMN-H]-·TRP and [FMN-H]-·GLU are observed to decay by non-statistical photodecay pathways, although the behaviour of [FMN-H]-·TRP is closer to statistical fragmentation. Long-lived FMN excited states (triplet) are therefore relatively quenched when TRP binds to [FMN-H]-. Importantly, we find that [FMN-H]-, [FMN-H]-·TRP and [FMN-H]-·GLU all decay predominantly via electron detachment following photoexcitation of the flavin chromophore, with amino acid complexation appearing not to inhibit this decay channel. The strong propensity for electron detachment is attributed to excited-state proton transfer within FMN, with proton transfer from a ribose alcohol to the phosphate preceding electron detachment.
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Affiliation(s)
- Kelechi O Uleanya
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.
| | - Cate S Anstöter
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.
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4
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Walter A, Eisenreich W, Storch G. Photochemical Desaturation and Epoxidation with Oxygen by Sequential Flavin Catalysis. Angew Chem Int Ed Engl 2023; 62:e202310634. [PMID: 37635656 DOI: 10.1002/anie.202310634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 08/23/2023] [Accepted: 08/24/2023] [Indexed: 08/29/2023]
Abstract
Catalytic desaturations are important strategies for the functionalization of organic molecules. In nature, flavoenzymes mediate the formation of α,β-unsaturated carbonyl compounds by concomitant cofactor reduction. Contrary to many laboratory methods for these reactions, such as the Saegusa-Ito oxidation, no transition metal reagents or catalysts are required. However, a molecular flavin-mediated variant has not been reported so far. We disclose a photochemical approach for silyl enol ether oxidation, which leads to α,β-unsaturated ketones (13 examples) in very good yields. The flavin catalysts are stable throughout the desaturation reaction, and we successfully applied them in a subsequent aerobic epoxidation by simply changing the reaction conditions. This protocol allowed us to directly convert silyl enol ethers into α,β-epoxyketones in a one-pot fashion (12 examples). Sequential flavin catalysis is not limited to one specific reactivity combination and can, inter alia, couple the photochemical oxidation with radical additions. We anticipate that flavin-catalyzed desaturation will be applicable to other substrate classes and that its sequential catalytic activity will enable rapid substrate diversification.
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Affiliation(s)
- Alexandra Walter
- School of Natural Sciences and Catalysis Research Center (CRC), Technical University of Munich (TUM), Lichtenbergstr. 4, 85747, Garching, Germany
| | - Wolfgang Eisenreich
- School of Natural Sciences and Catalysis Research Center (CRC), Technical University of Munich (TUM), Lichtenbergstr. 4, 85747, Garching, Germany
| | - Golo Storch
- School of Natural Sciences and Catalysis Research Center (CRC), Technical University of Munich (TUM), Lichtenbergstr. 4, 85747, Garching, Germany
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5
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Takeda A, Oka M, Iida H. Atom-Economical Syntheses of Dihydropyrroles Using Flavin-Iodine-Catalyzed Aerobic Multistep and Multicomponent Reactions. J Org Chem 2023. [PMID: 37183405 DOI: 10.1021/acs.joc.3c00444] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Herein, we report facile, atom-economical syntheses of multisubstituted 2,3-dihydropyrroles using flavin-iodine-catalyzed aerobic oxidative multistep transformations of chalcones with β-enamine ketones or 1,3-dicarbonyl compounds and amines. Exploiting coupled flavin-iodine catalysis, the multistep reaction, including C-C and C-N bond formation, is promoted only by the consumption of O2 (1 atm), thus allowing aerobic oxidative synthesis that generates green H2O as the only waste.
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Affiliation(s)
- Aki Takeda
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan
| | - Marina Oka
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan
| | - Hiroki Iida
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan
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6
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Pokluda A, Zubova E, Chudoba J, Krupička M, Cibulka R. Catalytic artificial nitroalkane oxidases - a way towards organocatalytic umpolung. Org Biomol Chem 2023; 21:2768-2774. [PMID: 36919409 DOI: 10.1039/d3ob00101f] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
Nitroalkane oxidases (NAOs) are flavoenzymes that catalyse the oxidation of nitroalkanes to their corresponding carbonyl compounds while producing nitrite anions. Herein, we present an artificial catalytic system using flavins or ethylene-bridged flavinium salts that works via an NAO-like process. Under conditions optimised in terms of solvent, base, temperature and oxygen pressure, primary nitroalkanes were transformed to aldehydes. In our system, aldehydes immediately reacted with other nitroalkane molecules to form β-nitroalcohols. The reduced flavin catalyst was re-oxidised by oxygen. An alternative mechanism towards β-nitroalcohols via 5-(2-nitrobutyl)-1,5-dihydroflavin was suggested through quantum chemical calculations and by trapping and characterising this dihydroflavin intermediate. Interestingly, 5-(2-nitrobutyl)-1,5-dihydroflavin is an analogue of the flavin adenine dinucleotide adduct previously observed in an NAO X-ray structure. In both mechanistic pathways, flavin-5-iminium species is formed by nitroalkanide addition to flavin. This process represents flavin-based umpolung of an original donor to an acceptor.
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Affiliation(s)
- Adam Pokluda
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague, Czech Republic.
| | - Ekaterina Zubova
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague, Czech Republic.
| | - Josef Chudoba
- Central Laboratories, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague, Czech Republic
| | - Martin Krupička
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague, Czech Republic.
| | - Radek Cibulka
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague, Czech Republic.
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7
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Shiogai Y, Oka M, Iida H. Aerobic cross-dehydrogenative coupling of toluenes and o-phenylenediamines by flavin photocatalysis for the facile synthesis of benzimidazoles. Org Biomol Chem 2023; 21:2081-2085. [PMID: 36804653 DOI: 10.1039/d3ob00113j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Herein, we demonstrate a green atom-economical synthesis of benzimidazoles via the flavin-photocatalysed aerobic oxidative cross-dehydrogenative coupling of toluenes and o-phenylenediamines. The proposed metal-free reaction proceeds in methanol/H2O under visible light irradiation by consuming only molecular oxygen from atmospheric air and produces only water as waste.
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Affiliation(s)
- Yuta Shiogai
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504 Japan.
| | - Marina Oka
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504 Japan.
| | - Hiroki Iida
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504 Japan.
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8
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Rehpenn A, Walter A, Storch G. Molecular Editing of Flavins for Catalysis. SYNTHESIS-STUTTGART 2021. [DOI: 10.1055/a-1458-2419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
AbstractThe diverse activity of flavoenzymes in organic transformations has fascinated researchers for a long time. However, when applied outside an enzyme environment, the isolated flavin cofactor only shows largely reduced activity. This highlights the importance of embedding the reactive isoalloxazine core of flavins in defined surroundings. The latter include crucial non-covalent interactions with amino acid side chains or backbone as well as controlled access to reactants such as molecular oxygen. Nevertheless, molecular flavins are increasingly applied in the organic laboratory as valuable organocatalysts. Chemical modification of the parent isoalloxazine structure is of particular interest in this context in order to achieve reactivity and selectivity in transformations, which are so far only known with flavoenzymes or even unprecedented. This review aims to give a systematic overview of the reported designed flavin catalysts and highlights the impact of each structural alteration. It is intended to serve as a source of information when comparing the performance of known catalysts, but also when designing new flavins. Over the last few decades, molecular flavin catalysis has emerged from proof-of-concept reactions to increasingly sophisticated transformations. This stimulates anticipating new flavin catalyst designs for solving contemporary challenges in organic synthesis.1 Introduction2 N1-Modification3 N3-Modification4 N5-Modification5 C6–C9-Modification6 N10-Modification7 Conclusion
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9
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Kitamura Y, Muramatsu S, Abe M, Inokuchi Y. Structural Investigation of Photochemical Intermediates in Solution by Cold UV Spectroscopy in the Gas Phase: Photosubstitution of Dicyanobenzenes by Allylsilanes. J Phys Chem A 2021; 125:6238-6245. [PMID: 34240866 DOI: 10.1021/acs.jpca.1c04807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Electrospray ion sources with an in-line quartz cell were constructed to produce photochemical intermediates in solution. These ion sources can detect photochemical intermediates having lifetimes longer than a few seconds. Intermediates formed by photosubstitution of 1,4-dicyanobenzene (DCB) by allyltrimethylsilane (AMS) in acetonitrile using a Xe lamp were injected into the mass spectrometer. The cationic intermediate (C11H10N2·H+) was observed at m/z = 171, but no anionic intermediate was found, although C11H9N2- was expected based on prior studies. Theoretical studies suggested that C11H9N2- was simultaneously converted to neutral C11H10N2 and cationic C11H10N2·H+ species, which can be stable intermediates in the photosubstitution reaction. The UV photodissociation (UVPD) spectrum of C11H10N2·H+ under cold (∼10 K) gas-phase conditions determined the conformation of the C11H10N2 unit of the C11H10N2·H+ cation. This report demonstrates that cold gas-phase UV spectroscopy is a prospectively powerful tool for investigation of the electronic and geometric structures of photochemical intermediates produced in solution.
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Affiliation(s)
- Yuma Kitamura
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - Satoru Muramatsu
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - Manabu Abe
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - Yoshiya Inokuchi
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
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10
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Pokluda A, Anwar Z, Boguschová V, Anusiewicz I, Skurski P, Sikorski M, Cibulka R. Robust Photocatalytic Method Using Ethylene‐Bridged Flavinium Salts for the Aerobic Oxidation of Unactivated Benzylic Substrates. Adv Synth Catal 2021. [DOI: 10.1002/adsc.202100024] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Adam Pokluda
- Department of Organic Chemistry University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
| | - Zubair Anwar
- Faculty of Chemistry Adam Mickiewicz University in Poznań Uniwersytetu Poznańskiego 8 61–614 Poznań Poland
| | - Veronika Boguschová
- Department of Organic Chemistry University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
| | - Iwona Anusiewicz
- Faculty of Chemistry University of Gdańsk Wita Stwosza 63 80–308 Gdańsk Poland
| | - Piotr Skurski
- Faculty of Chemistry University of Gdańsk Wita Stwosza 63 80–308 Gdańsk Poland
| | - Marek Sikorski
- Faculty of Chemistry Adam Mickiewicz University in Poznań Uniwersytetu Poznańskiego 8 61–614 Poznań Poland
| | - Radek Cibulka
- Department of Organic Chemistry University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
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11
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Tanimoto K, Okai H, Oka M, Ohkado R, Iida H. Aerobic Oxidative C-H Azolation of Indoles and One-Pot Synthesis of Azolyl Thioindoles by Flavin-Iodine-Coupled Organocatalysis. Org Lett 2021; 23:2084-2088. [PMID: 33656903 DOI: 10.1021/acs.orglett.1c00241] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The aerobic oxidative cross-coupling of indoles with azoles driven by flavin-iodine-coupled organocatalysis has been developed for the green synthesis of 2-(azol-1-yl)indoles. The coupled organocatalytic system enabled the one-pot three-component synthesis of 2-azolyl-3-thioindoles from indoles, azoles, and thiols in an atom-economical manner by utilizing molecular oxygen as the only sacrificial reagent.
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Affiliation(s)
- Kazumasa Tanimoto
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504, Japan
| | - Hayaki Okai
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504, Japan
| | - Marina Oka
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504, Japan
| | - Ryoma Ohkado
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504, Japan
| | - Hiroki Iida
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504, Japan
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12
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Hartman T, Reisnerová M, Chudoba J, Svobodová E, Archipowa N, Kutta RJ, Cibulka R. Photocatalytic Oxidative [2+2] Cycloelimination Reactions with Flavinium Salts: Mechanistic Study and Influence of the Catalyst Structure. Chempluschem 2021; 86:373-386. [DOI: 10.1002/cplu.202000767] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 12/22/2020] [Indexed: 01/19/2023]
Affiliation(s)
- Tomáš Hartman
- Department of Organic Chemistry University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
| | - Martina Reisnerová
- Department of Organic Chemistry University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
| | - Josef Chudoba
- Central Laboratories University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
| | - Eva Svobodová
- Department of Organic Chemistry University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
| | - Nataliya Archipowa
- Manchester Institute of Biotechnology and School of Chemistry The University of Manchester Manchester M1 7DN United Kingdom
| | - Roger Jan Kutta
- Institute of Physical and Theoretical Chemistry University of Regensburg 93040 Regensburg Germany
| | - Radek Cibulka
- Department of Organic Chemistry University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
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13
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Walter A, Storch G. Synthetic C6-Functionalized Aminoflavin Catalysts Enable Aerobic Bromination of Oxidation-Prone Substrates. Angew Chem Int Ed Engl 2020; 59:22505-22509. [PMID: 32790228 PMCID: PMC7756793 DOI: 10.1002/anie.202009657] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 08/08/2020] [Indexed: 12/19/2022]
Abstract
Flavoenzymes catalyze oxidations via hydroperoxide intermediates that result from activation of molecular O2. These reactions—such as hydroxylation and halogenation—depend on the additional catalytic activity of functional groups in the peptide environment of the flavin cofactor. We report synthetic flavin catalysts that contain C6 amino modifications at the isoalloxazine core and are consequently capable of mediating halogenations outside the peptide surrounding. The catalysts are competent in the selective, biomimetic bromination of oxidation‐prone phenols, flavones, and flavanones using a halide salt in combination with 2,6‐lutidinium oxalate as a flavin reductant under visible‐light irradiation. Our studies show the beneficial effect of stacked bisflavins as well as the catalytic activity of the flavin modifications. The designed flavin catalysts outperform isolated natural (−)‐riboflavin and contribute to the continuing search for tailored flavins in oxidation reactions.
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Affiliation(s)
- Alexandra Walter
- Department ChemieTechnische Universität MünchenLichtenbergstr. 485747GarchingGermany
| | - Golo Storch
- Department ChemieTechnische Universität MünchenLichtenbergstr. 485747GarchingGermany
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14
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Walter A, Storch G. Synthetische, C6‐funktionalisierte Aminoflavinkatalysatoren ermöglichen die aerobe Bromierung oxidationsanfälliger Substrate. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202009657] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Alexandra Walter
- Department Chemie Technische Universität München Lichtenbergstr. 4 85747 Garching Deutschland
| | - Golo Storch
- Department Chemie Technische Universität München Lichtenbergstr. 4 85747 Garching Deutschland
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15
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Oka M, Katsube D, Tsuji T, Iida H. Phototropin-Inspired Chemoselective Synthesis of Unsymmetrical Disulfides: Aerobic Oxidative Heterocoupling of Thiols Using Flavin Photocatalysis. Org Lett 2020; 22:9244-9248. [PMID: 33226236 DOI: 10.1021/acs.orglett.0c03458] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Inspired by the photochemical mechanism of a plant blue-light receptor, a unique flavin-based photocatalytic system was developed for the chemoselective heterocoupling of two different thiols, which enabled the facile synthesis of unsymmetrical disulfides. Owing to the redox- and photo-organocatalysis of flavin, the coupling reaction took place under mild metal-free conditions and visible light irradiation with the use of air, which is recognized as the ideal green oxidant.
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Affiliation(s)
- Marina Oka
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504 Japan
| | - Daichi Katsube
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504 Japan
| | - Takeshi Tsuji
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504 Japan
| | - Hiroki Iida
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504 Japan
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16
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Okai H, Tanimoto K, Ohkado R, Iida H. Multicomponent Synthesis of Imidazo[1,2-a]pyridines: Aerobic Oxidative Formation of C–N and C–S Bonds by Flavin–Iodine-Coupled Organocatalysis. Org Lett 2020; 22:8002-8006. [DOI: 10.1021/acs.orglett.0c02929] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Hayaki Okai
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan
| | - Kazumasa Tanimoto
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan
| | - Ryoma Ohkado
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan
| | - Hiroki Iida
- Department of Chemistry, Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan
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17
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Martínek M, Váňa J, Šebej P, Navrátil R, Slanina T, Ludvíková L, Roithová J, Klán P. Photochemistry of a 9‐Dithianyl‐Pyronin Derivative: A Cornucopia of Reaction Intermediates Lead to Common Photoproducts. Chempluschem 2020; 85:2230-2242. [DOI: 10.1002/cplu.202000370] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 07/12/2020] [Indexed: 12/15/2022]
Affiliation(s)
- Marek Martínek
- Department of Chemistry Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic
- RECETOX Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic
| | - Jiří Váňa
- Institute of Organic Chemistry and Technology Faculty of Chemical Technology University of Pardubice Studentská 573 532 10 Pardubice Czech Republic
| | - Peter Šebej
- RECETOX Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic
| | - Rafael Navrátil
- Department of Organic Chemistry Faculty of Science Charles University Hlavova 2030/8 128 43 Prague Czech Republic
| | - Tomáš Slanina
- Department of Chemistry Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic
- RECETOX Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic
| | - Lucie Ludvíková
- Department of Chemistry Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic
- RECETOX Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic
| | - Jana Roithová
- Institute for Molecules and Materials Radboud University Heyendaalseweg 135 6525 AJ Nijmegen The Netherlands
| | - Petr Klán
- Department of Chemistry Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic
- RECETOX Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic
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18
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Thapa P, Hazoor S, Chouhan B, Vuong TT, Foss FW. Flavin Nitroalkane Oxidase Mimics Compatibility with NOx/TEMPO Catalysis: Aerobic Oxidization of Alcohols, Diols, and Ethers. J Org Chem 2020; 85:9096-9105. [PMID: 32569467 DOI: 10.1021/acs.joc.0c01013] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Biomimetic flavin organocatalysts oxidize nitromethane to formaldehyde and NOx-providing a relatively nontoxic, noncaustic, and inexpensive source for catalytic NO2 for aerobic TEMPO oxidations of alcohols, diols, and ethers. Alcohols were oxidized to aldehydes or ketones, cyclic ethers to esters, and terminal diols to lactones. In situ trapping of NOx and formaldehyde suggest an oxidative Nef process reminiscent of flavoprotein nitroalkane oxidase reactivity, which is achieved by relatively stable 1,10-bridged flavins. The metal-free flavin/NOx/TEMPO catalytic cycles are uniquely compatible, especially compared to other Nef and NOx-generating processes, and reveal selectivity over flavin-catalyzed sulfoxide formation. Aliphatic ethers were oxidized by this method, as demonstrated by the conversion of (-)-ambroxide to (+)-sclareolide.
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Affiliation(s)
- Pawan Thapa
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019-0065, United States
| | - Shan Hazoor
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019-0065, United States
| | - Bikash Chouhan
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019-0065, United States
| | - Thanh Thuy Vuong
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019-0065, United States
| | - Frank W Foss
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019-0065, United States
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19
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Deazaflavin reductive photocatalysis involves excited semiquinone radicals. Nat Commun 2020; 11:3174. [PMID: 32576821 PMCID: PMC7311442 DOI: 10.1038/s41467-020-16909-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 06/02/2020] [Indexed: 11/30/2022] Open
Abstract
Flavin-mediated photocatalytic oxidations are established in synthetic chemistry. In contrast, their use in reductive chemistry is rare. Deazaflavins with a much lower reduction potential are even better suited for reductive chemistry rendering also deazaflavin semiquinones as strong reductants. However, no direct evidence exists for the involvement of these radical species in reductive processes. Here, we synthesise deazaflavins with different substituents at C5 and demonstrate their photocatalytic activity in the dehalogenation of p-halogenanisoles with best performance under basic conditions. Mechanistic investigations reveal a consecutive photo-induced electron transfer via the semiquinone form of the deazaflavin as part of a triplet-correlated radical pair after electron transfer from a sacrificial electron donor to the triplet state. A second electron transfer from the excited semiquinone to p-halogenanisoles triggers the final product formation. This study provides first evidence that the reductive power of excited deazaflavin semiquinones can be used in photocatalytic reductive chemistry. Flavins and deazaflavins are well suited for photoredox processes but their application in photoreductions is challenging. Here, the authors provide direct evidence of the high reductive power of excited deazaflavin semiquinones and their application in catalytic photodehalogenations.
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20
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Petsi M, Zografos AL. 2,5-Diketopiperazine Catalysts as Activators of Dioxygen in Oxidative Processes. ACS Catal 2020. [DOI: 10.1021/acscatal.0c01847] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Marina Petsi
- Department of Chemistry, Main University Campus, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
| | - Alexandros L. Zografos
- Department of Chemistry, Main University Campus, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
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21
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Zelenka J, Roithová J. Mechanistic Investigation of Photochemical Reactions by Mass Spectrometry. Chembiochem 2020; 21:2232-2240. [DOI: 10.1002/cbic.202000072] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 03/23/2020] [Indexed: 11/06/2022]
Affiliation(s)
- Jan Zelenka
- Department of Spectroscopy and CatalysisInstitute for Molecules and MaterialsRadboud University Nijmegen Heyendaalseweg 135 6525 AJ Nijmegen (The Netherlands
| | - Jana Roithová
- Department of Spectroscopy and CatalysisInstitute for Molecules and MaterialsRadboud University Nijmegen Heyendaalseweg 135 6525 AJ Nijmegen (The Netherlands
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22
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Topological Dynamics of a Radical Ion Pair: Experimental and Computational Assessment at the Relevant Nanosecond Timescale. CHEMISTRY 2020. [DOI: 10.3390/chemistry2020014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Chemical processes mostly happen in fluid environments where reaction partners encounter via diffusion. The bimolecular encounters take place at a nanosecond time scale. The chemical environment (e.g., solvent molecules, (counter)ions) has a decisive influence on the reactivity as it determines the contact time between two molecules and affects the energetics. For understanding reactivity at an atomic level and at the appropriate dynamic time scale, it is crucial to combine matching experimental and theoretical data. Here, we have utilized all-atom molecular-dynamics simulations for accessing the key time scale (nanoseconds) using a QM/MM-Hamiltonian. Ion pairs consisting of a radical ion and its counterion are ideal systems to assess the theoretical predictions because they reflect dynamics at an appropriate time scale when studied by temperature-dependent EPR spectroscopy. We have investigated a diketone radical anion with its tetra-ethylammonium counterion. We have established a funnel-like transition path connecting two (equivalent) complexation sites. The agreement between the molecular-dynamics simulation and the experimental data presents a new paradigm for ion–ion interactions. This study exemplarily demonstrates the impact of the molecular environment on the topological states of reaction intermediates and how these states can be consistently elucidated through the combination of theory and experiment. We anticipate that our findings will contribute to the prediction of bimolecular transformations in the condensed phase with relevance to chemical synthesis, polymers, and biological activity.
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23
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Tolba AH, Vávra F, Chudoba J, Cibulka R. Tuning Flavin-Based Photocatalytic Systems for Application in the Mild Chemoselective Aerobic Oxidation of Benzylic Substrates. European J Org Chem 2019. [DOI: 10.1002/ejoc.201901628] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Amal Hassan Tolba
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 166 28 Prague Czech Republic
| | - František Vávra
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 166 28 Prague Czech Republic
| | - Josef Chudoba
- Central Laboratories; University of Chemistry and Technology Prague; Technická 5 166 28 Prague Czech Republic
| | - Radek Cibulka
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 166 28 Prague Czech Republic
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24
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Zelenka J, Cibulka R, Roithová J. Flavinium Catalysed Photooxidation: Detection and Characterization of Elusive Peroxyflavinium Intermediates. Angew Chem Int Ed Engl 2019; 58:15412-15420. [PMID: 31364790 PMCID: PMC6852162 DOI: 10.1002/anie.201906293] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/08/2019] [Indexed: 12/18/2022]
Abstract
Flavin-based catalysts are photoactive in the visible range which makes them useful in biology and chemistry. Herein, we present electrospray-ionization mass-spectrometry detection of short-lived intermediates in photooxidation of toluene catalysed by flavinium ions (Fl+ ). Previous studies have shown that photoexcited flavins react with aromates by proton-coupled electron transfer (PCET) on the microsecond time scale. For Fl+ , PCET leads to FlH.+ with the H-atom bound to the N5 position. We show that the reaction continues by coupling between FlH.+ and hydroperoxy or benzylperoxy radicals at the C4a position of FlH.+ . These results demonstrate that the N5-blocking effect reported for alkylated flavins is also active after PCET in these photocatalytic reactions. Structures of all intermediates were fully characterised by isotopic labelling and by photodissociation spectroscopy. These tools provide a new way to study reaction intermediates in the sub-second time range.
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Affiliation(s)
- Jan Zelenka
- Department of Spectroscopy and CatalysisInstitute for Molecules and MaterialsRadboud University NijmegenHeyendaalseweg 1356525AJNijmegenThe Netherlands
| | - Radek Cibulka
- Department of organic chemistryFaculty of Chemical TechnologyUniversity of Chemistry and Technology PragueTechnická 5166 28Prague 6Czech Republic
| | - Jana Roithová
- Department of Spectroscopy and CatalysisInstitute for Molecules and MaterialsRadboud University NijmegenHeyendaalseweg 1356525AJNijmegenThe Netherlands
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